Field
This document relates to a slot antenna which is applicable to a variety of information terminal apparatuses and formed directly on a conductive housing of the information terminal apparatus, and an information terminal apparatus using the same.
Related Art
A slot antenna is a type of antenna that has a long, slim slot formed on a wide conductor plate and causes the slot to emit radio waves. The slot antenna has a number of limitations when used in a small-sized, portable information terminal such as a laptop computer. The slot antenna is known in U.S. Laid-Open Patent NOs. 2004-0257283 and 2005-0146475, U.S. Pat. Nos. 6,339,400 and 6,686,886, and Korean Laid-Open Patent No. 10-2012-0044229. The slot antenna structure disclosed in U.S. Laid-Open Patent NOs. 2004-0257283 and 2005-0146475 cannot be implemented because lowering the display housing leads to a shortage of slot antenna design space and a narrower bandwidth.
The laptop computer comprises a main body equipped with a keyboard, a touchpad, etc and a display unit rotatably mounted to the main body via a hinge and incorporating a liquid crystal display panel. The publicly known slot antenna is formed on a PCB (printed circuit board) and embedded in the main body or display unit.
If the housing (hereinafter, referred to as “display housing”) of the display unit in the laptop computer is non-conductive, the slot antenna cannot be formed directly in the display housing. When manufacturing a slot antenna on the PCB and embedding the PCB in the display unit above the hinge of the laptop computer, the PCB should be spaced enough away from the liquid crystal display panel to achieve a high radiation efficiency. As such, it is necessary to secure enough space between the PCB where the slot antenna is formed and the liquid crystal display panel. The display unit of the laptop computer tends to be slimmer in design. Due to this, it is difficult for the display unit of the laptop computer to have space for the PCB with the slot antenna.
Embedding the PCB with the slot antenna in the display unit of the laptop computer may lower the radiation efficiency of the slot antenna due to the liquid crystal display panel. Common electrodes, pixel electrodes, etc formed on the entire surface of the liquid crystal display panel are formed of a transparent electrode material such as ITO (Indium Tin Oxide). An ITO film partially absorbs the energy radiated from the slot antenna and causes a reduction in radiation efficiency. The farther the slot antenna is from the ITO film, the better the radiation efficiency. For this reason, locating the PCB with the slot antenna on the back side of the liquid crystal display panel lowers the radiation efficiency because of the ITO film. Accordingly, when embedding the PCB with the slot antenna in the display unit of the laptop computer, the ITO film should be removed partially from the liquid crystal display panel in order to provide distance between the slot antenna and the ITO film. This approach incurs additional processes and costs in partially removing the ITO film.
If the display housing of the laptop computer is manufactured as a metal housing, and the PCB with the slot antenna is installed within the display housing, the metal housing interrupts the radiation energy from the slot antenna. In this case, the metal housing cannot even act as a reflector since its distance from the slot antenna is very short.
If the PCB with the slot antenna is installed in the main body housing of the laptop computer, the user's hands touching the keyboard and the touch pad may decrease the slot antenna performance. That is, when the user's hands move closer to the slot antenna, the resonance frequency of the slot antenna changes and therefore the slot antenna does not operate at a desired frequency and interrupts communication between electronic devices. When a great deal of energy radiated from the slot antenna is absorbed into the user's hands, the radiation energy becomes significantly weaker, making communication between electronic devices difficult. For example, call quality may be good or poor depending on which part of the phone the user grips, like the death grip problem with Apple's Iphones.